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General |
Two types of gabions are required for the Works: -Gabion boxes (the tenns baskets and crates are synonymous); -Gabion mattresses. Gabions and mattresses are available .in a wide range of standard sizes. The size and type of wire mesh, diaphragms binding wires, and selvedge wire are specified in the following paragraphs. The fabric of the gabions shall be triple twisted hexagonal woven steel wire mesh. The wire shall be galvanized before weaving. All wire used in the manufacture and tying of gabion shall comply with the BS.1052: 1980 "Mild steel wire for general engineering purposes" and shall be galvanized in accordance with BS 443: 1982 "Specifications for testing zinc coatings on steel wire and for quality requirements."
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Mesh |
The gabion boxes shall have hexagonal woven mesh with a maximum size of 10 cm x 12 cm, with the joints fonned by twisting each pair of wires through three half turns. Wire used for the fonnation of the mesh panel will have a diameter of 3.0mm.
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Wire
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The diameter of the wire used in the fabrication of the mesh shall be 3.0 mm. Sufficient binding and tie wires, horizontal and vertical bracers, and other accessories needed for the assembly and erection of the gabion works shall be supplied, at no additional cost, by the Contractor. The quantity of such wire shall be not less than 10% by weight of the gabions supplied under this Contract. The diameter of the binding and connection wires shall be 2.4 mm.
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Galvanizing
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All wire used in the manufacture of gabion boxes and in the wiring operations during construction shall be heavily coated with zinc. The minimum weight of zinc coating shall be as follows:
The adhesion of the zinc coating to the wire shall be strong enough of an extent that when the wire is wrapped six turns around a mandrel of four times the diameter of the wire, it does not flake or crack to such an extent that any zinc can be easily removed by rubbing with the bare fingers. |
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Selvedges
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All edges of the gabion boxes including end-panel and diaphragms shall be mechanically selvedged in such a way to prevent unraveling of the mesh. The selvedge shall be of a wire having a diameter of 3.9 mm. |
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Diaphragms
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Diaphragms shall be supplied to divide each gabion unit into cells to control movement of fill material within the gabion. The diaphragm to be provided shall be equally spaced at a distance of 1 m along the length of the gabion. The diaphragms shall be selvedge to a diameter of 3.9 mm.
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Gabions Mattresses |
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Mesh
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The gabion mattresses shall be triple twisted hexagonal woven steel wire mesh of size 6cm x 8cm. The mattresses shall be divided by internal diaphragms into compartments of 1 m width. |
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Foundations |
The ground on which the gabions are to be founded shall be trimmed by hand to form a plane surface before placing the baskets, Where shown on the drawing or ordered by the Project Manager the gabions mattresses shall be laid on a graded filter or an approved geotextile, Filtered material shall consist of graded rock of a dense, sound quality free from weathering or mechanical weakness, The size and grading shall be such that the filter will be retained by the rock in the gabion and will itself retain the finer particles of the adjacent general filling, If necessary the filter shall be placed in successive layers of different grading, reducing in particle size from the gabions to the general filing, The completed filter layer shall be such that it shall represent a dense mass well consolidated and not subject to settlement
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Fixing |
After placing in position and before filling, the gabions shall be stretched to their full size and shall be stretched to their full size and shall be wired to the adjoining row at the top and bottom edges and at the corners. |
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Stone Fill
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Stone for filling gabions shall be between 120 mm and 250 mm dia stone, It shall be hard and resistant to abrasion, uniform in texture and sound, without cracks or other imperfections likely to impair resistance to weathering,
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